Calendar and scheduling applications and services generally organize and display a user's activities, tasks, jobs, appointments, meetings, and other types of events. They may also provide event reminders or notifications that are presented to a user based on the date and time of an event. Existing services may be limited to presenting or triggering a reminder at the time of an event, a default time period before the event, or at some time period specified by a user, which may or may not provide enough advance notice to the user. Some approaches to triggering reminders are based on geofencing and/or detecting communication with an individual associated with a reminder.